Currently also experiencing the issue with an AMD R9 280.

Mesa and LLVM versions:

$ glxinfo | grep Mesa
client glx vendor string: Mesa Project and SGI
OpenGL core profile version string: 4.5 (Core Profile) Mesa 18.2.2
OpenGL version string: 4.4 (Compatibility Profile) Mesa 18.2.2
OpenGL ES profile version string: OpenGL ES 3.2 Mesa 18.2.2

$ glxinfo | grep LLVM
Device: AMD TAHITI (DRM 2.50.0, 4.18.10-arch1-1-ARCH, LLVM 7.0.0) (0x679a)
OpenGL renderer string: AMD TAHITI (DRM 2.50.0, 4.18.10-arch1-1-ARCH, LLVM
7.0.0)

Sure would appreciate a fix for this, it worked fine on this same system when
the game came out.